The present invention relates to a piezoelectric vibrator unit where internal electrodes are laminated in parallel to a deforming axis of the vibrator, and in particular to the structure of the internal electrode, and also related to an ink jet recording head comprising the piezoelectric vibrator.
As is disclosed in Japanese Patent Publication No. 4-1052A, for an ink jet recording head employing a piezoelectric vibrator in a vertical vibration mode, an elastic plate is located with a narrow gap from the rear face of a nozzle plate in which a plurality of nozzles are formed, and piezoelectric vibrators having a piezoelectric constant d31 are brought into contact with the rear face of the elastic plate, so that the vibrators correspond to pressure generating chambers that are formed in a channel forming substrate.
With this arrangement, a drive signal is transmitted to the piezoelectric vibrators, and ink is led from a reservoir via an ink supply port to the pressure generating chambers. Then, transmission of a drive signal is halted, and the piezoelectric vibrators are expanded to exert pressure to the ink. As a result, ink droplets can be ejected from the nozzle orifices.
For such a recording head, multiple piezoelectric vibrators must be arranged at the pitches at which the nozzle orifices are arranged. Therefore, as in, for example, Japanese Patent Publication No. 7-195688A, one end of a single piezoelectric vibrator plate is fixed to a base, and slits are formed into strips from the free end to the area that is fixed to the base, so that the recording head is provided as a unit where multiple piezoelectric vibrators are fixed to the same base.
In each of the piezoelectric vibrators having a piezoelectric constant d31, a discrete internal electrode is exposed at the tip of only the free end, and a common internal electrode is exposed only at the rear end of the fixed area. A plurality of these electrodes are layered with piezoelectric material in between. The discrete internal electrodes are connected to a segment electrode for transmitting a signal for driving the piezoelectric vibrators, while the common internal electrodes are connected in common by a connection part that is formed in the fixed area, and are connected to common electrodes. The piezoelectric vibrators are connected via the segment electrodes and the common electrodes to an external driver.
However, to reduce manufacturing costs, the width of the fixed area must be so narrow that the piezoelectric vibrators can be mechanically secured. Thus, the connection area for the common internal electrode that connects the individual piezoelectric vibrators in common is short, and the resistance in the common connection area is increased. In addition, there is another problem that heat is generated due to Joule heat. To resolve these shortcomings, the width of the fixed area can be increased. However, a new problem will occur, such as warping during annealing, or increase in the material cost.
Further, the discrete internal electrodes of the drive piezoelectric vibrators are connected to the segment electrodes that are so formed as to be extended from the distal end to the fixed area of the piezoelectric vibrators, and the common internal electrodes are connected via a flexible cable to the common electrodes that are so formed as to be extended from the rear end to the fixed area of the dummy piezoelectric vibrators. With this arrangement, a drive signal is transmitted from an external drive circuit.
Therefore, this piezoelectric vibrators, or so-called dummy piezoelectric vibrators that are formed at least on the side end faces of the piezoelectric vibrators and that do not relate to ejection of ink droplets, are to be formed by cutting the end of a single piezoelectric vibrator plate, a first conductive layer, which is extended from the distal end to the obverse face and which serves as a segment electrode, and a second conductive layer, which is extended from the rear end to the obverse face and that serves as a common electrodes separate from the first conductive layer, must be formed in advance, and the process for forming these first and second conductive layers requires laboring costs.